| Summary: | The threat of illicit trafficking of special nuclear material (SNM) has brought about an interest in detection methods capable of identifying high-Z material in a non-invasive fashion on relatively short timescales. Muon Scattering Tomography (MST) is a method by which information about the material content of a cargo container can be obtained by measuring cosmic ray muons before and after passing through the container. In this way significant quantities of SNM that are being illegally shipped at freight ports can be detected. In a real-life application, it is important for practical reasons that containers carrying SNM can be identified swiftly, on a time scale of minutes. MST requires large detectors above and below the volume of interest. Resistive plate chambers (RP Cs ) were chosen for this, which have good spatial and timing resolution, good hit finding efficiency, and can be produced on large scales. RPC prototypes were built, and the performance of these RPCs is detailed, together with the software framework developed for the analysis of the detector data. Two novel detection algorithms were developed, intended to find SNM hidden in cargo containers. In order to test the algorithms, a simulation study with large-scale detectors tuned to the performance of the RPCs was performed. A wide range of cargo was simulated in this study based on real-life cargo data, showing the performance of the new algorithms in terms of the fraction of containers can be cleared in a given time frame. It is shown that 84% of all containers can be cleared in a minute or less, showing that the methods meet the design goals. An application of the developed methods to 3D imaging of legacy nuclear waste drums is also shown. Here, longer scan times are possible, and dimensions on the order of centimeters can be resolved inside concrete-filled waste drums.
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